In recent years, because of the limited reserves of petroleum on Earth, green energy technology has been developed quickly. Particularly, solar energy is one of the main research subjects because it is easy to obtain and does not cause environmental pollution when used to generate electricity.
Referring to FIGS. 1 and 2, a first conventional solar power system includes a plurality of solar panels 11, and a power adjusting device 12 that includes a voltage converting circuit 121. The solar panels 11 are electrically connected in series in order to generate a total output voltage that is higher than an output voltage of a single one of the solar panels 11. However, when one of the solar panels 11 malfunctions due to aging or is broken (e.g., the solar panel 111 in FIG. 1), the solar panels 11 form an open circuit and cannot operate normally. When some of the solar panels 11 are covered, for example by a shadow 112 of tree leaves or by bird's droppings 113, total current generated by the solar panels 11 is reduced so that power generating efficiency of the first conventional solar power system drops.
To overcome the above problems, a second conventional solar power system is provided (see FIG. 3). The second conventional solar power system is shown to be similar to the first solar power system, and also includes a plurality of the solar panels 11 and the power adjusting device 12 including the voltage converting circuit 121. The only difference from the first conventional solar power system is that the solar panels 11 of the second conventional solar power system are electrically connected in parallel with one another. With this configuration, the conventional solar power system can still operate when one of the solar panels 11 malfunctions, but the total current generated by the solar panels 11 as well as the power generating efficiency of the first conventional solar system will be reduced. Further, the problem of reduction of the total current generated by the solar panels 11 with some of them being covered remains unsolved.
To further improve the first and second solar power systems, a third conventional solar power system is provided (see FIG. 4). The third conventional solar power system further includes a plurality of diodes 122. Each of the diodes 122 is electrically connected between a respective one of the solar panel 11 and the power adjusting device 12. By virtue of the diodes 122, output current of an abnormal one of the solar panels 11 which generates electricity with efficiency (output voltage) lower than other solar panels 11 cannot flow through a corresponding one of the diodes 122. Therefore, the abnormal solar panel 11 does not negatively affect overall output voltage outputted by the third conventional solar power system. However, when most of the solar panels 11 operate abnormally or are covered, they are disconnected from the power adjusting device 12 by corresponding ones of the diodes 122 and do not provide output current to the power adjusting device 12. Consequently, the power generating efficiency of the third conventional solar system significantly drops.